PHOTOFRAGMENTATION OF NOCL IN A MOLECULAR-BEAM AT 193 NM - A BIMODAL VIBRATIONAL-STATE DISTRIBUTION

The 193 nm photodissociation of NOCl has been studied by photofragment translational spectroscopy under collisionless conditions. Time-of-flight (TOF) distributions of the Cl and NO fragments were measured at various detection angles and different laser polarizations. The overall vibrational distribution of the NO fragments was found to extend from nu" = 0 to, at least, nu" = 24, consisting of two distributions, both centered at around nu" = 15. The broad distribution (DELTA-nu" almost-equal-to 24), having a recoil anisotropy beta = 0.45, and the narrow one (DELTA-nu" almost-equal-to 8) with beta = 0.95, emerge from different reaction channels, i.e. potential energy surfaces of NOCl which evince different vibrational coupling strengths. The results are interpreted in terms of an initial excitation of two close-lying electronic states of A' symmetry.